The following is a US Mint press release
acknowledging that error coins were accidently released by the US Mint
in 2007.

Presidential dollar coins have a somewhat
unique feature where the mottos "In God We Trust", E Pluribus Unum" and
the year and mint mark are on the coin's edge. A special
manufacturing process is used to apply the edge lettering.
Evidently, at least one batch of presidential dollars missed this step
in the process and made it into circulation.

"Press Release and Public Statements
March 7, 2007

A
Statement from the United States Mint

The United States Mint has struck more than 300 million George
Washington Presidential $1 Coins. We have recently learned that an
unspecified quantity of these coins inadvertently left the United States
Mint at Philadelphia without edge-lettering on them. It is unknown how
many of these coins without inscriptions on the edge have been placed
into circulation.

The United States Mint understands the importance of the inscriptions
“In God We Trust” and “E Pluribus Unum,” as well as the mint mark and
year on U.S. coinage. We take this matter seriously. We also consider
quality control a high priority. The agency is looking into the matter
to determine a possible cause in the manufacturing process.

Production of the Presidential $1 Coin, with its unique edge-lettering,
is a new, complex, high volume manufacturing system, and the United
States Mint is determined to make technical adjustments to perfect the
process. As we adjust this new process,
we intend to eliminate any such defects.

Consistent with the agency’s practice in such situations, the United
States Mint has informed the Office of Inspector General of the U.S.
Department of the Treasury about this matter. "

Currently, these Plain edge error
presidential dollars are trading between $100 and $300 per coin,
depending on condition.